Silver powder is used, for example, for electrodes and circuit formation in various electronic components, such as internal electrodes of multi-layer capacitors, conductor patterns for circuit boards, and electrodes for plasma display panel substrates. In recent years, silver powder is also used, for example, for light-shielding materials for inner layers of IC cards and magnetic cards, as well as for formation of cover-up parts of scratch cards, printing for various security purposes, and formation of fine-line circuits.
As an example of silver powder used for such electroconductive materials, Patent Literature 1 discloses a dendritic silver powder obtained according to an electroless wet process, the dendritic particulate silver powder having a D10 of 3.0 nm or less, a D50 of 12.0 nm or less, a D90 of 18.0 nm or less, and a Dmax of 44.0 nm or less, as measured according to laser diffraction/scattering particle size distribution measurement.
Patent Literature 2 discloses a dendritic silver powder having a specific surface area of 0.5-4 m2/g as measured by the BET single-point method, wherein the shape of each silver powder particle observed by an electron microscope at a magnification of 5000 or 10000 includes a rod-shaped trunk and acicular branches extending from the trunk as rod-shaped branches, or acicular branches wherein some of the branches are bent in the middle.
Various methods for producing silver powder are known, such as: an electrolytic method wherein an electrolytic solution including silver ions is electrolyzed to cause silver particles to deposit on an electrode (see Patent Literature 3); a method for obtaining a highly-dispersive spherical silver powder by a wet reduction process of producing a silver ammine complex aqueous solution with a silver nitrate solution and ammonia water, and then adding thereto an organic reducing agent, as disclosed in Patent Literature 4; and a method employing a chemical reduction method in which, for example, a reaction is caused by adding, to a silver sulfate aqueous solution, polyvinyl pyrrolidone and one of sodium phosphinate, formaldehyde, and hydroquinone as reducing agents, as disclosed in Patent Literature 5.